Preventing commutator noises in radio



April 15, 1930. E, GAGE 1,754,622

Patented Apr. 15, 1930 V UNITED STATES PATENT OFFICE .nDwARiJ G. GAGE, or BROOKLYN, NEW YORK, ASSIGNOR r RADIO PATENTS com ronATro v, or NEW YORK, N. Y.

' PREVENTING GOMMUTATOIt NOISES IN IBiA'DIO Application filed March 23,1923; Serial No. 627,002.

This invention relates to the production of improved current for radio apparatus and has special reference to the provision of improved sources of energy for such apparatus although the invention may have other applications than to radio.

As is well known, the filament of an electron tube employed in a .radio receiving set, is energized by direct current and usually from a battery, as it has been found that dynamically generated current has variations which produce objectionable noises in the receiver and render it unsuitable. Storage batteries are usually employed as the frequent renewals required make primary batteries too expensive and the ,frequent' charging of the storage battery is expensive and very inconvenient. 2

The main object of the present invention is to remove objectionable variations from dynamically generated or other commutated current,.and this is accomplished by causing the current variations or-commutatorlripple, caused by the action of the commutator, to be of a frequency outside of the audible range. Other and ancillary objects of the invention will appear hereinafter.

The accompanying drawing, which illustrates the invention, is a diagram of electrical apparatus embodying the invention.

Referring to the drawings the generator, of the constant voltage type, comprises the usual field pole pieces 1 and 2 embracing the 5 rotatable armature of the gramme ring type having the usual ring core 3 with the armature winding 4; suitably connected 'in a wellknown manner by commutator leads 5 with the segments of the commutator 6 upon which bear the brushes 7 and 8. One of the brushes 8 is connected through a variable induction coil 9 to one terminal of the filament 10 of anaudion electrontube having the 5 usual grid 11 and plate 12, the other terminal of the filament being connected with the brush, 7. The filament is thus connected in series with the induction coil 9v between the brushes 7 and 8 The generaton operates after the well known manner of direct curment 10.

The commutation of the electro-motive force generated in the armature coil does not result in an absolutely constant potential, but the curve of the electro-motive force .as impressed upon the exterior circuit is serrated with indentations so that this curve of electro-motive force shows an electro-motive force of constant value having superposed thereon a comparatively slight variable electro-motive force.- This slight variable electro-motive force is so relatively insignificant in such uses as power and light circuits that it may be neglected, butin the excitation of the filaments of electron tubes it is suflicient to cause objectionable noises. This slight variable electro-motive force depends for amplitude upon the number of commutator segments, and for its frequency upon the number of commutator segments and the number of revolutions per minute of the commutator. It is desirable to reduce the amplitude of'the variable element of the electromotive force'as above referred to and so it is desirable that the number of commutator segments be large, but as it is the object of the dynamo of the drawing to maintain the frequency of this variable element or .commutator ripple below the audible frequency (approximately sixteen per second) the speed must be made correspondingly low. As the speed is one of the elements determinin the magnitude of the whole electro-motive orce. the reduction in speed may be compensated for by increasing the diameter of the armature, whereby the peripheral speed or conductor speed of the armature is increased, the

ally four volts for an audion tube) but such that the frequency of the commutator ripple is sub-audible. The result is that ohjectionable noises produced in the apparatus by commutator ripples within the limits of audible frequencies are avoided. The noises may also be avoided by making the ripple frequency above the upper limit of audibility or ultra audible as well as below the lower limit of audibility or sub-audible. An example of a suitable arrangement for giving a sub-audible frequency of the commutator ripple is 48 commutator bars and 10 revolutions per minute, the number and speed of the armature conductors and thestrength of the field magnets being proportioned according- 1y as is understood in the art, to give the desired Voltage.

The inductance coil 9 is for the purpose of smoothing out sharp variations in the'ripples. With some sources of current and commutating means such sharp varia ions may occur which would cause second ry frequencies which might be within the audible range although the primary, frequency of the ripple would be outside that range. In such cases the coil would be almost indispensable in removing the ripple noise but in cases where the ripple is a sine wave or other smooth curve the coil might bedispensed with although at all times it has a smoothing influence on any variations and is therefore desirable.

Vhile the invention has been illustrated in what is considered its best application it may have other embodiments Without departing from its spirit and is not therefore limited to the structure shown in the drawing.

What I claim is:

The method of generating an-eifectively smooth direct current with a commutator machine having a plurality of alternating current sources and corresponding commutator segments consisting in running the commutator at such a speed that the frequency of commutator ripple is below the limit of audibility.

In testimony whereof I have signed this specification this 21st day of March, 1923.

EDWARD G. GAGE. 

